The pS2 protein in colorectal carcinomas and metastases

Expression of pS2 protein in 50 primary tumors, metastases and recurrent tumors of colorectal carcinomas has been analyzed by immunohistochemistry. Sixty percent of the primary tumors were at least focally positive for the antigen. There was no correlation between pS2 expression and histologic grade of the lesions. In contrast, pS2 expression in T4 and T3 tumors was significantly higher than in T2 carcinomas. Immunoreactions in carcinomas with distant metastases (MI) were stronger than in M0 cases. However, this difference did not reach statistical significance. The presence of lymph node metastases did not correlate with pS2 expression. High expression of pS2 in T4 and T3 carcinomas together with the finding of pronounced expression of the antigen at invasion fronts in single cases could be interpreted as a function in tumor cell invasion and motility. However, in metastases and recurrent tumors, pS2 expression did not differ from primary lesions (53% positive lesions). All in all, under consideration of the latter finding in particular and together with the randomly distributed immunopositive tumor cells and cell clusters in the majority of cases, it is more likely that the expression pattern of pS2 in colorectal carcinomas is a result of overall tumor cell heterogeneity.